Anne Giedinghagen wanted desperately to stay in school. Having struggled with depression and anorexia since the sixth grade, the rail-thin Cornell junior was meeting regularly with a therapist at the university's counseling center in Ithaca, N.Y. But late last fall, when she told her therapist about her increasingly strong urge to kill herself, Giedinghagen received an ultimatum from the school she loved so much: she had to get better or she would have to leave. So she did what any crafty 20-year-old would do. She tried to carve out a third option--feigning improvement by, as she put it, acting "as normal...